1. Field of the Invention
The present invention relates to heat-resistant exhaust manifolds and methods of preparing such manifolds. More particularly, the present invention relates to a method of lining an exhaust manifold with a heat-resistant compound containing zirconium, a ceramic material, or both, and a heat-resistant manifold which is the product of the described process.
2. Prior Art
In the automotive industry, it has long been recognized that heat generated by the combustion process emanating from the exhaust manifolds into the engine compartment of a vehicle is a problem. Not only does such heat degrade the various components in the engine compartment which are not heat resistant, but the heat also causes the exhaust manifolds themselves to become brittle and deteriorate. The problem is exacerbated in today's smaller engine compartments since cars are being "down-sized", especially when a high-performance engine is packed tightly into such a small engine compartment, e.g., a turbocharged or supercharged engine. Heat loss from exhaust manifolds is not limited to such high-performance engines, however.
Many varied types of heat shields and insulation have been employed in the prior attempts to alleviate this problem. Ongoing effort continue to channel the maximum possible amount of heat which has been generated in the combustion chambers, from the exhaust ports of the cylinder heads out into and through the exhaust system, minimizing the amount which is released in the engine compartment.
Another reason for wishing to channel the maximum amount of heat possible through the exhaust system is that by retaining heat in the exhaust system, "light off" of the catalytic converter may be achieved sooner if more heat is conveyed directly to the converter. This promotes greater fuel efficiency as well as lowered exhaust emissions, which are both high priorties in today's market.